A user interface is a very important part of an electronic device. How easy and comfortable the user uses the interface for controlling the electronic device may ultimately determine the usefulness, acceptance and user experience of the electronic device. There have been numerous interaction methods between user and user interface, and new interaction methods are continuously being developed. Human nature determines that the most natural interaction between a person and an external object is through the human skin. Therefore, it would be preferred if a user interface could be so designed that it seamlessly integrates with a user's skin layer and it responds to contorting of the skin for communicating signals. Such an interface is further preferred if the operation of the interface does not affect or compromise the user's ordinary gesture and behavior.
When a flat elastic object, such as a thin sheet of rubber (an analogue to human skin), is bent or stretched under an applied external force, it forms a complex deformed shape. Such a deformed shape contains information about the intensity and direction of the external force. By monitoring the deformed shape in real time, it is possible to obtain dynamic information of the deformation process under the external force. Measuring values such as strain, pressure and flexure of a three-dimensional (3D) object normally requires a complex set of sensors placed on the object. Conventional systems for measuring conformation of mechanical objects are based either on an array of strain gauges or on optical scanning methods. In these methods, miniaturization and integration levels are relatively low. In the case of using strain gauges, potential for portability of the measuring device is limited. In the case of using optical scanning methods, digitalized readings from the distinct sensors are used as a basis for computing the conformation based on a model of the mechanical structure. The computation of the conformation depends on the complexity of the system and the number of degrees of freedom. Furthermore, optical systems (e.g. cameras) require certain length to focus on the monitored object, which limits the operational size of the system and requires the camera to be placed outside of the monitored object.
Therefore, what is needed is a sensor module for sensing complex 3D flexural deformations that has high miniaturization and integration levels for being used in portable electronic devices.
This disclosure, in general, relates to design and manufacturing of a sensor module that is capable of detecting complex 3D flexural deformation of an object. For the purpose of utilizing the concept of the present invention, it is assumed that such an object has a large surface area that is subject to compressing, bending, stretching, folding, etc. For example, such an object may be a flat sheet (rubber or plastic), a cylinder, or a sphere. The sensor module utilizes piezoelectric effect of a material, and an optimum arrangement of the material is achieved with the help of nanotechnologies and manipulation capabilities of the material at micrometer to nanometer scale (referred to as nanoscale hereinafter). With the high miniaturization and integration levels, the sensor module can be used, for example, as a user interface or a sensing unit for portable electronic devices. As a particular application, the sensor module of the present invention may be used for gesture recognition and hand/finger movement tracking.